Random tiny egg from grown hen?

[ChickenHawk12]

We have 6 RIRs that are almost a year old, and 3 BO's that are 2.5 years old. The BOs don't seem to be good layers, as we usually only get 6 eggs per day, sometimes 7. I think only 1 is laying anymore, and 1 I don't think ever laid eggs.

Today I found this one tiny egg. Why would that happen? They are old to be laying eggs like this, no?

About a month or so ago, we switched from a 16% protein to an 18% feather fixer, as I had noticed a drop in production and healthy appearance when our regular food producer dropped from 18% to 16%, and I read that BO's really need a bit extra protein due to being a heavy breed with a lot of feathering.

Could that increase in protein have gotten out dud BO to actually start laying at 2.5 years old?

I'm perplexed

 

[AlleysChicks]

Little egg looks like a RIR egg to me. It may be a fairy egg.

 

[ChickenMammX4]

We get a tiny egg from our full grown hens from time to time.